How are old erythrocytes (red blood cells) removed from the blood and disposed of?

Red blood cells live for about 120 days. They are then removed from the blood stream in the spleen and liver, by macrophages, white blood cells that "eat" other cells.

Once "eaten", the different parts of the red blood cells are recycled.

The globine part (protein) of the hemaglobin is broken down into amino acids, which are returned to the blood.
The iron in the heme group is removed and bound to specific proteins, that will store the iron for later use.
The rest of the heme group is broken down into bilirubin, a yellowish orangy pigment. In the liver, the bilirubin is put into bile, that is then released in the intestinal tract. This pigment is what gives stool its brown color.